This invention relates to a circuit for generating a digital signal, and, more particularly, to a circuit for generating a digital signal in a utilization position in response to a remote switch command.
There are many useful applications where a plurality of different digital signals must be transmitted to a remote utilization position. For example, in a multi-channel hand-held tranceiver system, a control unit adapted to be held by one hand is coupled by a cable to a separate tranceiver chassies. A channel scan system is provided. It includes two kinds of manual switches mounted in the control unit housing. When one switch is depressed, upward channel select is carried out, and when the other switch is depressed downward channel select is carried out. When two switches are depressed at the same time, the channel selection to the emergency channel is effected. The digital signals representing these operation commands are transmitted from the control unit through the cable to a channel select PLL circuit in the main chassies. In such a case that a plurality of the signal conditions are transmitted to the remote utilization position with relatively good S/N ratio, many problems occur. One of the most important problems is in the use of digital signal transmission lines, specifically if a multiconductor cable is used, the cost of the cable is increased. Further, when the digital signals are transmitted in level transition, the S/N ratio is deteriorated depending on the transmission characteristic of the cable.